In the field of internal combustion engines for vehicles, for example, there has been proposed an apparatus for controlling an internal combustion engine in such a manner as to achieve a torque output and a vehicle acceleration corresponding to an accelerator operation of the driver as described in Japanese Unexamined Patent Publication Nos. 2003-120349 and 2003-170759.
In the patent documents cited above, in order to calculate a control amount for achieving a target drive force such as a target torque, actual engine speed is used as one of parameters. However, even if actual torque approaches or coincides with target torque in accordance with this control, a comparatively long dead time is required until the engine speed actually reaches a level corresponding to the target torque. Accordingly, if a control amount is calculated based on the actual engine speed, hunting of the engine may be generated during the driving of the internal combustion engine.
In order to prevent the hunting from occurring, it is possible to determine target rotational speed corresponding to a target drive force of an internal combustion engine drive system by using a model as a preset internal combustion engine model or an output transmission model and determine a control amount based on the target rotational speed. However, such a model represents a standard or average relation and does not necessarily match an actual individual internal combustion engine or output transmission system with high precision. Accordingly, deviation may occur between the engine speed actually reached and the target rotational speed at steady state, which can reduce the precision of various controls.